The Page tab on the Script Builder enables you to override the default URL of the page being viewed.  You can also override the Page Title and the URL of the referring page if you wish.

By default, the Maropost web tracking script only stores the domain and path of the web page being viewed.  Query string parameters appended to the page URL are not stored.

However, if you are using query string parameters to control the actual page that is being viewed, then you will certainly want to override the default behavior.

page_url

In the above example, the full URL of the web page is being passed to the web tracking script.